Imaging lens

ABSTRACT

A compact low-cost imaging lens which provides brightness with an F-value of 2.5 or less and a wide field of view and corrects aberrations properly, meeting the demand for low-profileness. The imaging lens elements are arranged in the following order from an object side to an image side: a first lens with positive refractive power having a convex surface on the object side; a second lens with negative refractive power; a third lens with positive or negative refractive power having at least one aspheric surface; a fourth lens with positive refractive power; a fifth lens as a meniscus double-sided aspheric lens having a concave surface near an optical axis on the image side; and a sixth lens as a meniscus lens having a concave surface near the optical axis on the object side. The both surfaces of the fifth lens have pole-change points off the optical axis.

The present application is based on and claims priority of Japanesepatent application No. 2013-266442 filed on Dec. 25, 2013, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to imaging lenses which form an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in a compact image pickup device, and more particularly toimaging lenses which are built in image pickup devices mounted inincreasingly compact and low-profile smart phones and mobile phones,PDAs (Personal Digital Assistants), game consoles, information terminalssuch as PCs, and home appliances with a camera function.

Description of the Related Art

In recent years, there has been a general tendency that most informationterminals have a camera function. Also, home appliances with a camerafunction have been introduced into the market; for example, a user whois away from home can see in real time what is going on at home, throughthe camera mounted in a home appliance by telecommunication between thehome appliance and his/her smart phone. It is thought that productswhich enhance consumer convenience by adding a camera function to aninformation terminal or home appliance will be increasingly developed inthe future. In addition, the camera mounted in such a product isexpected to not only provide high resolution to cope with an increase inthe number of pixels but also be compact and low-profile and providehigh brightness and a wide field of view. In particular, the imaginglens to be built in a mobile terminal is strongly expected to below-profile enough to be applicable to a low-profile product.

However, in order to provide a low-profile imaging lens with a widefield of view and high brightness as described above, the followingproblem has to be addressed: difficulty in correcting aberrations in theperipheral area of the image and ensuring high imaging performancethroughout the image.

Conventionally, for example, the imaging lenses described inJP-A-2010-026434 (Patent Document 1) and JP-A-2011-085733 (PatentDocument 2) are known as compact high-resolution imaging lenses.

Patent Document 1 discloses an imaging lens composed of five constituentlenses, which includes, in order from an object side, a positive firstlens, a positive second lens, a negative third lens, a positive fourthlens, and a negative fifth lens and features compactness and highbrightness with an F-value of about 2 and corrects various aberrationsproperly.

Patent Document 2 discloses an imaging lens which includes a first lensgroup including a first lens having a convex surface on an object side,a second lens group including a second lens having a concave surface onan image side, a third lens group including a meniscus third lens havinga concave surface on the object side, a fourth lens group including ameniscus fourth lens having a concave surface on the object side, and afifth lens group including a meniscus fifth lens having an asphericsurface with an inflection point on the object side. This imaging lensis intended to realize a compact lens system with high resolution.

The imaging lens described in Patent Document 1, composed of fiveconstituent lenses, corrects various aberrations properly and provideshigh brightness with an F-value of about 2.0 to about 2.5; however, itstotal track length is longer than the diagonal length of the effectiveimaging plane of the image sensor, bringing about a disadvantage inmaking the imaging lens low-profile. Furthermore, if this lensconfiguration is designed to provide a wide field of view, it will bedifficult to correct aberrations in the peripheral area of the imageproperly.

The imaging lens described in Patent Document 2 has a lens system whichis relatively low-profile and able to correct aberrations properly.However, in order to ensure brightness with an F-value of 2.8 or lessand a field of view of 65 degrees or more, the problem of difficulty incorrecting aberrations in the peripheral area of the image must beaddressed.

As stated above, in conventional technology, it is difficult to providea low-profile imaging lens with a wide field of view which provides highbrightness and high resolution.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problem, and anobject thereof is to provide a compact low-cost imaging lens which meetsthe demand for low-profileness in spite of an increase in the number ofconstituent lenses and offers high brightness with an F-value of 2.5 orless and a wide field of view and corrects various aberrations properly.

Here, the term “low-profile” implies that the total track length isshorter than the diagonal length of the effective imaging plane of theimage sensor, and the term “wide field of view” implies that the fieldof view is 70 degrees or more. The diagonal length of the effectiveimaging plane of the image sensor is twice the maximum image height, inwhich the maximum image height means the vertical height from an opticalaxis to the position where a light ray incident on the imaging lens at amaximum field of view enters the image plane.

According to one aspect of the present invention, there is provided animaging lens which forms an image of an object on a solid-state imagesensor, in which elements are arranged in the following order from anobject side to an image side: a first lens with positive refractivepower having a convex surface on the object side; a second lens withnegative refractive power; a third lens with positive or negativerefractive power having at least one aspheric surface; a fourth lenswith positive refractive power; a fifth lens as a meniscus double-sidedaspheric lens having a concave surface near an optical axis on the imageside; and a sixth lens as a meniscus lens having a concave surface nearthe optical axis on the object side. The both surfaces of the fifth lenshave pole-change points off the optical axis.

In the imaging lens with the above configuration, the first lens and thefourth lens have relatively strong positive refractive power to offer alow-profile design. The second lens with negative refractive powerproperly corrects spherical aberrations and chromatic aberrations whichoccur on the first lens. The third lens with positive or negativerefractive power, having at least one aspheric surface, corrects axialchromatic aberrations, high-order spherical aberrations, comaaberrations, and field curvature properly. In the fifth lens, the bothsurfaces are aspheric surfaces having pole-change points off the opticalaxis so that the shape of its image-side surface changes from a concaveshape near the optical axis to a convex shape at the lens periphery andthe shape of its object-side surface changes from a convex shape nearthe optical axis to a concave shape at the lens periphery. Therefore,the fifth lens corrects field curvature in the image peripheral area,corrects distortion, and properly controls the angle of a chief rayincident on the image sensor from the image center to the imageperipheral area. The sixth lens is responsible for the final correctionof field curvature, distortion and the incidence angle of a chief ray. A“pole-change point” here means a point on an aspheric surface at which atangential plane intersects the optical axis perpendicularly.

When the above configuration is adopted and refractive power isappropriately distributed to the constituent lenses, the imaging lenscan be a low-profile high-performance imaging lens. Since all theconstituent lenses are located with an air gap from an adjacent element,a relatively large number of aspheric surfaces can be used, therebymaking it easier to realize an imaging lens which corrects aberrationsproperly.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (1) below:0.5<f1/f<1.5  (1)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f1: focal length of the first lens.

The conditional expression (1) defines an appropriate range for theratio of the focal length of the first lens to the focal length of theoverall optical system of the imaging lens, and indicates a condition tooffer a low-profile design and suppress spherical aberrationsattributable to a low F-value and a wide field of view. If the value isabove the upper limit of the conditional expression (1), the refractivepower of the first lens would be too weak to offer a low-profile design.On the other hand, if the value is below the lower limit of theconditional expression (1), the refractive power of the first lens wouldbe too strong to suppress high-order spherical aberrations.

More preferably, the imaging lens satisfies a conditional expression(1a) below:0.5<f1/f<1.20.  (1a)

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (2) below:−2.0<f2/f<−0.5  (2)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f2: focal length of the second lens.

The conditional expression (2) defines an appropriate range for theratio of the focal length of the second lens to the focal length of theoverall optical system of the imaging lens, and indicates a condition tooffer a low-profile design and properly correct chromatic aberrationsand other various aberrations attributable to a low F-value and a widefield of view. If the value is above the upper limit of the conditionalexpression (2), the negative refractive power of the second lens wouldbe too strong to offer a low-profile design and make it difficult tocorrect coma aberrations and distortion in the peripheral portion. Onthe other hand, if the value is below the lower limit of the conditionalexpression (2), the negative refractive power of the second lens wouldbe too weak to correct axial chromatic aberrations.

More preferably, the imaging lens satisfies a conditional expression(2a) below:−1.5<f2/f<−0.8.  (2a)

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (3) below:0.3<f4/f<1.0  (3)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f4: focal length of the fourth lens.

The conditional expression (3) defines an appropriate range for theratio of the focal length of the fourth lens to the focal length of theoverall optical system of the imaging lens, and indicates a condition tooffer a low-profile design and correct spherical aberrations and comaaberrations properly. If the value is above the upper limit of theconditional expression (3), the positive refractive power of the fourthlens would be too weak to offer a low-profile design though it would beadvantageous in correcting spherical aberrations and coma aberrations.On the other hand, if the value is below the lower limit of theconditional expression (3), the refractive power of the fourth lenswould be too strong to correct spherical aberrations and comaaberrations though it would be advantageous in offering a low-profiledesign.

More preferably, the imaging lens satisfies a conditional expression(3a) below:0.4<f4/f<1.0.  (3a)

Preferably, in the imaging lens according to the present invention, thefifth lens has negative refractive power, and a conditional expression(4) below is satisfied:−1.5<f5/f<−0.3  (4)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f5: focal length of the fifth lens.

The conditional expression (4) defines an appropriate range for theratio of the focal length of the fifth lens to the focal length of theoverall optical system of the imaging lens, and indicates a condition tooffer a low-profile design and correct various aberrations. If the valueis above the upper limit of the conditional expression (4), the negativerefractive power of the fifth lens would be too strong to offer alow-profile design and correct chromatic aberrations properly. On theother hand, if the value is below the lower limit of the conditionalexpression (4), the negative refractive power of the fifth lens would betoo weak to correct coma aberrations and field curvature properly thoughit would be advantageous in offering a low-profile design.

More preferably, the imaging lens satisfies a conditional expression(4a) below:−1.5<f5/f<−0.5.  (4a)

Preferably, in the imaging lens according to the present invention, thesixth lens has negative refractive power, and a conditional expression(5) below is satisfied:−3.0<f6/f<−0.8  (5)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f6: focal length of the sixth lens.

The conditional expression (5) defines an appropriate range for theratio of the focal length of the sixth lens to the focal length of theoverall optical system of the imaging lens, and indicates a condition tooffer a low-profile design and correct various aberrations. If the valueis above the upper limit of the conditional expression (5), the negativerefractive power of the sixth lens would be too strong to offer alow-profile design. On the other hand, if the value is below the lowerlimit of the conditional expression (5), the negative refractive powerof the sixth lens would be too weak to correct distortion and fieldcurvature though it would be advantageous in offering a low-profiledesign.

More preferably, the imaging lens satisfies a conditional expression(5a) below:−2.6<f6/f<−1.0.  (5a)

Preferably, in the imaging lens according to the present invention, thethird lens has a meniscus shape with a convex surface near the opticalaxis on the object side.

Since the third lens has a meniscus shape, field curvature can becorrected more effectively.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (6) below:0.3<r4/f<1.0  (6)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   r4: curvature radius of the image-side surface of the second        lens.

The conditional expression (6) defines an appropriate range for thecurvature radius of the image-side surface of the second lens withrespect to the focal length of the overall optical system of the imaginglens, and indicates a condition to correct axial chromatic aberrationsproperly and suppress an increase in the manufacturing error sensitivityof the second lens. If the value is above the upper limit of theconditional expression (6), the negative refractive power of theimage-side surface of the second lens would be too weak to correctchromatic aberrations. On the other hand, if the value is below thelower limit of the conditional expression (6), the negative refractivepower of the image-side surface of the second lens would be too strong,resulting in an increase in manufacturing error sensitivity and makingit difficult to maintain stable performance.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (7) and (8) below:20<νd1−νd2<50  (7)50<νd3,νd4,νd5,νd6<80  (8)

where

νd1: Abbe number of the first lens at d-ray

νd2: Abbe number of the second lens at d-ray

νd3: Abbe number of the third lens at d-ray

νd4: Abbe number of the fourth lens at d-ray

νd5: Abbe number of the fifth lens at d-ray

νd6: Abbe number of the sixth lens at d-ray.

The conditional expression (7) defines an appropriate range for thedifference between the Abbe number of the first lens and the Abbe numberof the second lens, and indicates a condition to correct chromaticaberrations properly. The conditional expression (8) defines anappropriate range for the Abbe number of each of the third lens to thesixth lens to enable the use of low-dispersion material in order tosuppress chromatic aberrations of magnification. When plastic materialwhich satisfies the conditional expressions (7) and (8) is adopted, theimaging lens can be manufactured at low cost.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (9) and (10) below:1.0<(r9+r10)/(r9−r10)<2.7  (9)−1.5<(r11+r12)/(r11−r12)<−0.5  (10)

where

-   -   r9: curvature radius of the object-side surface of the fifth        lens    -   r10: curvature radius of the image-side surface of the fifth        lens    -   r11: curvature radius of the object-side surface of the sixth        lens    -   r12: curvature radius of the image-side surface of the sixth        lens.

The conditional expression (9) defines an appropriate range for thecurvature radii of the fifth lens to determine the paraxial shape of thefifth lens, and indicates a condition to correct chromatic aberrationsproperly and suppress an increase in lens manufacturing errorsensitivity. If the value is above the upper limit of the conditionalexpression (9), the negative refractive power of the fifth lens would betoo weak to correct chromatic aberrations. On the other hand, if thevalue is below the lower limit of the conditional expression (9), therefractive power of the image-side surface of the fifth lens would betoo strong, undesirably resulting in an increase in manufacturing errorsensitivity.

The conditional expression (10) defines an appropriate range for thecurvature radii of the sixth lens to determine the paraxial shape of thesixth lens, and indicates a condition to correct chromatic aberrationsand field curvature while keeping the imaging lens low-profile. If thevalue is above the upper limit of the conditional expression (10), therefractive power of the object-side surface of the sixth lens would betoo strong to correct field curvature. On the other hand, if the valueis below the lower limit of the conditional expression (10), therefractive power of the sixth lens would weaken, resulting in a tendencytoward worsening of chromatic aberrations, though it would beadvantageous in offering a low-profile design.

More preferably, the imaging lens satisfies conditional expressions (9a)and (10a) below:1.4<(r9+r10)/(r9−r10)<2.5  (9a)−1.3<(r11+r12)/(r11−r12)<−0.8.  (10a)

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (11) below:0.3<f4/f1<1.5  (11)

where

-   -   f1: focal length of the first lens    -   f4: focal length of the fourth lens.

The conditional expression (11) defines an appropriate range for theratio of the focal length of the fourth lens to the focal length of thefirst lens, and indicates a condition to offer a low-profile design andprovide a low F-value and a wide field of view. The positive refractivepower of the fourth lens is controlled so that the first lens is notcompelled to have excessively strong positive refractive power. Bybalancing the focal lengths of the two lenses within the range definedby the conditional expression (11), a low F-value and a wide field ofview can be realized.

More preferably, the imaging lens satisfies a conditional expression(11a) below:0.4<f4/f1<1.1.  (11a)

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the general configuration of animaging lens in Example 1;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1;

FIG. 3 is a schematic view showing the general configuration of animaging lens in Example 2;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2;

FIG. 5 is a schematic view showing the general configuration of animaging lens in Example 3;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3;

FIG. 7 is a schematic view showing the general configuration of animaging lens in Example 4;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4;

FIG. 9 is a schematic view showing the general configuration of animaging lens in Example 5;

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5;

FIG. 11 is a schematic view showing the general configuration of animaging lens in Example 6; and

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail referring to the accompanying drawings. FIGS. 1, 3,5, 7, 9, and 11 are schematic views showing the general configurationsof the imaging lenses in Examples 1 to 6 according to this embodiment,respectively. Since all these examples have the same basic lensconfiguration, the general configuration of an imaging lens according tothis embodiment is explained below referring to the schematic view ofExample 1.

As shown in FIG. 1, the imaging lens according to the present inventionincludes, in order from an object side to an image side, a first lens L1with positive refractive power having a convex surface on the objectside, a second lens L2 with negative refractive power, a third lens L3with positive or negative refractive power having at least one asphericsurface, a fourth lens L4 with positive refractive power, a fifth lensL5 as a meniscus double-sided aspheric lens having a concave surfacenear an optical axis X on the image side, and a sixth lens L6 as ameniscus lens having a concave surface near the optical axis X on theobject side. The both aspheric surfaces of the fifth lens L5 havepole-change points off the optical axis X. An aperture stop ST islocated on the object side of the first lens L1. A filter IR such as aninfrared cut filter is located between the sixth lens L6 and an imageplane IMG. The filter IR is omissible. In the present invention, totaltrack length and back focus are each defined as a distance on theassumption that the filter IR is removed.

In the imaging lens with the above configuration, the first lens L1 andthe fourth lens L4 have relatively strong positive refractive power tooffer a low-profile design. The first lens L1 has a meniscus shape witha convex surface on the object side, and the fourth lens L4 has ameniscus shape with a convex surface on the image side. Alternatively,the first lens L1 may have a biconvex shape and in this case, thepositive refractive power can be distributed to the both surfaces tosuppress spherical aberrations effectively. The second lens L2, havingnegative refractive power, properly corrects spherical aberrations andchromatic aberrations which occur on the first lens L1. The third lensL3 has the weakest positive or negative refractive power among theconstituent lenses of the imaging lens, and at least one asphericsurface thereof properly corrects axial chromatic aberrations,high-order spherical aberrations, coma aberrations, and field curvature.The fifth lens L5 has a meniscus shape with a concave surface near theoptical axis X on the image side, and both its surfaces are asphericsurfaces having pole-change points off the optical axis X. Thus, theshape of the image-side surface of the fifth lens L5 changes from aconcave shape near the optical axis X to a convex shape at the lensperiphery, and the shape of its object-side surface changes from aconvex shape near the optical axis X to a concave shape at the lensperiphery. These aspheric surfaces correct field curvature in the imageperipheral area, correct distortion, and properly control the angle of achief ray incident on the image plane IMG from the image center to theimage peripheral area. The sixth lens L6 is responsible for the finalcorrection of field curvature, distortion and the incidence angle of achief ray.

In order to enhance the telecentricity of the imaging lens and make theimaging lens low-profile, the aperture stop ST is located on the objectside of the first lens L1. Specifically, it is located between theintersection of the object-side surface of the first lens L1 with theoptical axis X and the periphery of the object-side surface of the firstlens L1.

Since the third lens L3 has a meniscus shape with a convex surface nearthe optical axis X on the object side, field curvature is corrected moreeffectively.

When the above configuration is adopted and refractive power isappropriately distributed to the constituent lenses, the imaging lenscan be a low-profile high-performance imaging lens with a low F-valueand a wide field of view. All the constituent lenses are located with anair gap from an adjacent element. This means that all the constituentlens surfaces can be aspheric and thus it is easy to enhance theaberration correction effect by the use of aspheric surfaces.

The imaging lenses according to this embodiment satisfy conditionalexpressions (1) to (11) below:0.5<f1/f<1.5  (1)−2.0<f2/f<−0.5  (2)0.3<f4/f<1.0  (3)−1.5<f5/f<−0.3  (4)−3.0<f6/f<−0.8  (5)0.3<r4/f<1.0  (6)20<νd1−νd2<50  (7)50<νd3,νd4,νd5,νd6<80  (8)1.0<(r9+r10)/(r9−r10)<2.7  (9)−1.5<(r11+r12)/(r11−r12)<−0.5  (10)0.3<f4/f1<1.5  (11)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f1: focal length of the first lens L1    -   f2: focal length of the second lens L2    -   f4: focal length of the fourth lens L4    -   f5: focal length of the fifth lens L5    -   f6: focal length of the sixth lens L6    -   r4: curvature radius of the image-side surface of the second        lens L2    -   νd1: Abbe number of the first lens L1 at d-ray    -   νd2: Abbe number of the second lens L2 at d-ray    -   νd3: Abbe number of the third lens L3 at d-ray    -   νd4: Abbe number of the fourth lens L4 at d-ray    -   νd5: Abbe number of the fifth lens L5 at d-ray    -   νd6: Abbe number of the sixth lens L6 at d-ray    -   r9: curvature radius of the object-side surface of the fifth        lens L5    -   r10: curvature radius of the image-side surface of the fifth        lens L5    -   r11: curvature radius of the object-side surface of the sixth        lens L6    -   r12: curvature radius of the image-side surface of the sixth        lens L6.

As for the refractive power of the first lens L1, when the conditionalexpression (1) is satisfied, the positive refractive power of the firstlens L1 is in an appropriate range so as to offer a low-profile designand suppress spherical aberrations.

As for the refractive power of the second lens L2, when the conditionalexpression (2) is satisfied, the negative refractive power of the secondlens L2 is in an appropriate range so as to offer a low-profile designand correct chromatic aberrations, and coma aberrations and distortionin the peripheral portion properly.

As for the refractive power of the fourth lens L4, when the conditionalexpression (3) is satisfied, the positive refractive power of the fourthlens L4 is in an appropriate range so as to offer a low-profile designand correct spherical aberrations and coma aberrations properly.

As for the refractive power of the fifth lens L5, when the conditionalexpression (4) is satisfied, the negative refractive power of the fifthlens L5 is in an appropriate range so as to offer a low-profile designand correct coma aberrations and field curvature properly.

As for the refractive power of the sixth lens L6, when the conditionalexpression (5) is satisfied, the negative refractive power of the sixthlens L6 is in an appropriate range so as to offer a low-profile designand correct distortion and field curvature properly.

As for the curvature radius of the image-side surface of the second lensL2, when the conditional expression (6) is satisfied, the curvatureradius of the image-side surface of the second lens L2 with respect tothe focal length of the overall optical system of the imaging lens is inan appropriate range so as to correct axial chromatic aberrationsproperly and suppress an increase in the manufacturing error sensitivityof the second lens L2.

As for the Abbe numbers of the first lens L1 and the second lens L2,when the conditional expression (7) is satisfied, the difference betweenthe Abbe number of the first lens L1 and the Abbe number of the secondlens L2 is in an appropriate range so as to correct chromaticaberrations properly.

As for the Abbe numbers of the third lens L3 to the sixth lens L6, whenthe conditional expression (8) is satisfied, low-dispersion material isused for the third lens L3 to the sixth lens L6, so it is easy tosuppress chromatic aberrations of magnification.

By selecting plastic material which satisfies the conditionalexpressions (7) and (8), the imaging lens can be manufactured at lowcost.

As for the paraxial shape of the fifth lens L5, when the conditionalexpression (9) is satisfied, chromatic aberrations are correctedproperly and an increase in the manufacturing error sensitivity of thefifth lens L5 is suppressed.

As for the paraxial shape of the sixth lens L6, when the conditionalexpression (10) is satisfied, the imaging lens is kept low-profile andchromatic aberrations and field curvature are corrected properly.

As for the ratio of the focal length of the fourth lens L4 to the focallength of the first lens L1, when the conditional expression (11) issatisfied, the positive refractive power of the first lens L1 and thepositive refractive power of the fourth lens L4 are appropriatelybalanced and the positive refractive power of the fourth lens L4 iscontrolled so that the positive refractive power of the first lens L1 isnot compelled to be excessively strong. Thus, aberrations aresuppressed, and the imaging lens can provide a low F-value and a widefield of view.

In this embodiment, all the lens surfaces are aspheric. The asphericshapes of these lens surfaces are expressed by Equation 1, where Zdenotes an axis in the optical axis direction, H denotes a heightperpendicular to the optical axis, k denotes a conic constant, and A4,A6, A8, A10, A12, A14, and A16 denote aspheric surface coefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R^{2\;}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, examples of the imaging lens according to this embodiment will beexplained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, ih denotes a maximum image height, TLA denotes totaltrack length with the filter IR removed, and bf denotes back focus withthe filter IR removed. i denotes a surface number counted from theobject side, r denotes a curvature radius, d denotes the distance on theoptical axis between lens surfaces (surface distance), Nd denotes arefractive index at d-ray (reference wavelength), and νd denotes an Abbenumber at d-ray. As for aspheric surfaces, an asterisk (*) after surfacenumber i indicates that the surface concerned is an aspheric surface.

Example 1

The basic lens data of Example 1 is shown in Table 1 below.

TABLE 1 Example 1 in mm f = 3.03 Fno = 2.2 ω (°) = 37.0 ih = 2.30 TLA =3.65 bf = 0.92 Surface Data Curvature Surface Refractive Abbe SurfaceNo. i Radius r Distance d Index Nd Number vd (Object Surface) InfinityInfinity  1 (Stop) Infinity −0.155  2* 1.3421 0.428 1.544 55.57  3*27.1744 0.058  4* 7.8700 0.190 1.635 23.91  5* 1.8165 0.171  6* 1.80160.231 1.535 56.16  7* 2.6007 0.425  8* −1.9249 0.477 1.544 55.57  9*−0.6143 0.017 10* 2.7974 0.285 1.535 56.16 11* 0.7122 0.258 12* −3.46430.195 1.535 56.16 13* −89.9982 0.150 14 Infinity 0.210 1.517 64.20 15Infinity 0.631 Image Plane Infinity Constituent Lens Data Lens StartSurface Focal Length 1 2 2.581 2 4 −3.765 3 6 9.964 4 8 1.471 5 10−1.877 6 12 −6.745 Aspheric Surface Data 2nd Surface 3rd Surface 4thSurface 5th Surface 6th Surface 7th Surface k 4.059E−01 0.000E+000.000E+00 −1.901E+01 0.000E+00 0.000E+00 A4 −5.184E−02 −3.080E−01−5.306E−01 −1.049E−01 −4.490E−01 −1.814E−01 A6 6.259E−02 1.952E+003.570E+00 1.608E+00 4.557E−01 1.438E−02 A8 −5.653E−01 −7.994E+00−1.227E+01 −4.242E+00 −5.831E−01 −2.130E−01 A10 6.498E−01 1.798E+012.451E+01 6.137E+00 1.130E+00 4.676E−01 A12 9.296E−01 −2.561E+01−3.265E+01 −6.943E+00 −8.414E−01 0.000E+00 A14 −2.958E+00 1.557E+012.091E+01 4.411E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10thSurface 11th Surface 12th Surface 13th Surface k 0.000E+00 −4.452E+000.000E+00 −8.959E+00 0.000E+00 0.000E+00 A4 8.579E−02 −2.844E−01−3.134E−01 −2.230E−01 4.489E−02 −6.882E−03 A6 4.806E−02 3.402E−015.972E−02 1.048E−01 −2.651E−03 0.000E+00 A8 −7.654E−02 −1.496E−011.988E−02 −4.726E−02 −4.166E−05 0.000E+00 A10 −1.554E−01 1.020E−01−1.261E−02 1.489E−02 −3.777E−05 0.000E+00 A12 1.153E−01 −6.663E−023.362E−03 −2.397E−03 0.000E+00 0.000E+00 A14 0.000E+00 7.988E−03−3.499E−04 6.854E−05 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00

As shown in Table 2 below, the imaging lens in Example 1 satisfies allthe conditional expressions (1) to (11).

TABLE 2  (1) 0.5 < f1/f < 1.5 0.85  (2)−2.0 < f2/f < −0.5 −1.24  (3)0.3< f4/f < 1.0 0.48  (4)−1.5 < f5/f < −0.3 −0.62  (5)−3.0 < f6/f < −0.8−2.22  (6)0.3 < r4/f < 1.0 0.60  (7)20 < vd1 − vd2 < 50 31.66  (8)50 <vd3, vd4, vd5, vd6 < 80 vd3 56.16 vd4 55.57 vd5 56.16 vd6 56.16  (9)1.0< (r9 + r10)/(r9 − r10) < 2.7 1.68 (10)−1.5 < (r11 + r12)/(r11 − r12) <−0.5 −1.08 (11)0.3 < f4/f1 < 1.5 0.57

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at wavelengths of g-ray (436 nm), F-ray(486 nm), e-ray (546 nm), d-ray (588 nm), and C-ray (656 nm). Theastigmatism diagram shows the amount of aberration at d-ray on sagittalimage surface S and the amount of aberration at d-ray on tangentialimage surface T (the same is true for FIGS. 4, 6, 8, 10, and 12). Asshown in FIG. 2, each aberration is corrected properly.

In Example 1, total track length TLA is 3.65 mm and TLA/(2ih) is 0.795,which suggests that the imaging lens is low-profile though it uses sixconstituent lenses. Also, the imaging lens offers a wide field of viewof 70 degrees or more and high brightness with an F-value of 2.2.

Example 2

The basic lens data of Example 2 is shown in Table 3 below.

TABLE 3 Example 2 in mm f = 3.04 Fno = 2.2 ω (°) = 37.0 ih = 2.30 TLA =3.66 bf = 0.83 Surface Data Curvature Surface Refractive Abbe SurfaceNo. i Radius r Distance d Index Nd Number vd (Object Surface) InfinityInfinity  1 (Stop) Infinity −0.155  2* 1.3712 0.423 1.544 55.57  3*49.1997 0.060  4* 11.0752 0.190 1.635 23.91  5* 1.8771 0.173  6* 1.84650.259 1.535 56.16  7* 3.0454 0.467  8* −2.0561 0.456 1.544 55.57  9*−0.6508 0.015 10* 2.5948 0.294 1.535 56.16 11* 0.7385 0.300 12* −2.89050.195 1.535 56.16 13* −90.0000 0.100 14 Infinity 0.210 1.517 64.20 15Infinity 0.591 Image Plane Infinity Constituent Lens Data Lens StartSurface Focal Length 1 2 2.586 2 4 −3.588 3 6 8.159 4 8 1.571 5 10−2.044 6 12 −5.590 Aspheric Surface Data 2nd Surface 3rd Surface 4thSurface 5th Surface 6th Surface 7th Surface k 5.571E−01 0.000E+000.000E+00 −2.084E+01 0.000E+00 0.000E+00 A4 −4.837E−02 −2.804E−01−5.243E−01 −1.318E−01 −4.676E−01 −1.808E−01 A6 4.875E−02 1.987E+003.689E+00 1.604E+00 4.493E−01 −8.288E−03 A8 −6.311E−01 −7.920E+00−1.225E+01 −4.081E+00 −6.092E−01 −2.339E−01 A10 8.322E−01 1.780E+012.420E+01 5.876E+00 1.121E+00 4.838E−01 A12 9.253E−01 −2.560E+01−3.265E+01 −6.945E+00 −8.324E−01 0.000E+00 A14 −2.960E+00 1.558E+012.091E+01 4.410E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10thSurface 11th Surface 12th Surface 13th Surface k 0.000E+00 −4.522E+000.000E+00 −8.535E+00 0.000E+00 0.000E+00 A4 1.167E−01 −2.441E−01−3.291E−01 −2.069E−01 5.831E−02 −1.760E−02 A6 7.914E−05 3.403E−017.882E−02 1.020E−01 −8.707E−03 2.740E−03 A8 −4.749E−02 −1.683E−012.119E−02 −4.357E−02 −4.684E−04 −9.983E−04 A10 −1.382E−01 9.569E−02−1.331E−02 1.414E−02 2.170E−04 5.743E−05 A12 1.045E−01 −6.569E−023.003E−03 −3.037E−03 0.000E+00 0.000E+00 A14 0.000E+00 1.404E−02−8.969E−04 2.777E−04 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00

As shown in Table 4 below, the imaging lens in Example 2 satisfies allthe conditional expressions (1) to (11).

TABLE 4  (1) 0.5 < f1/f < 1.5 0.85  (2)−2.0 < f2/f < −0.5 −1.18  (3)0.3< f4/f < 1.0 0.52  (4)−1.5 < f5/f < −0.3 −0.67  (5)−3.0 < f6/f < −0.8−1.84  (6)0.3 < r4/f < 1.0 0.62  (7)20 < vd1 − vd2 < 50 31.66  (8)50 <vd3, vd4, vd5, vd6 < 80 vd3 56.16 vd4 55.57 vd5 56.16 vd6 56.16  (9)1.0< (r9 + r10)/(r9 − r10) < 2.7 1.80 (10)−1.5 < (r11 + r12)/(r11 − r12) <−0.5 −1.07 (11)0.3 < f4/f1 < 1.5 0.61

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4, eachaberration is corrected properly.

In Example 2, total track length TLA is 3.66 mm and TLA/(2ih) is 0.797,which suggests that the imaging lens is low-profile though it uses sixconstituent lenses. Also, the imaging lens offers a wide field of viewof 70 degrees or more and high brightness with an F-value of 2.2.

Example 3

The basic lens data of Example 3 is shown in Table 5 below.

TABLE 5 Example 3 in mm f = 3.04 Fno = 2.2 ω (°) = 37.0 ih = 2.30 TLA =3.66 bf = 0.83 Surface Data Curvature Surface Refractive Abbe SurfaceNo. i Radius r Distance d Index Nd Number vd (Object Surface) InfinityInfinity  1 (Stop) Infinity −0.155  2* 1.3713 0.431 1.544 55.57  3*−90.0000 0.058  4* 14.5069 0.190 1.635 23.91  5* 1.9120 0.177  6* 1.95270.258 1.535 56.16  7* 3.1512 0.443  8* −2.0531 0.470 1.544 55.57  9*−0.6543 0.017 10* 2.5456 0.290 1.535 56.16 11* 0.7499 0.302 12* −2.71050.195 1.535 56.16 13* −88.9484 0.100 14 Infinity 0.210 1.517 64.20 15Infinity 0.592 Image Plane Infinity Constituent Lens Data Lens StartSurface Focal Length 1 2 2.488 2 4 −3.489 3 6 8.934 4 8 1.579 5 10−2.107 6 12 −5.233 Aspheric Surface Data 2nd Surface 3rd Surface 4thSurface 5th Surface 6th Surface 7th Surface k 5.659E−01 0.000E+000.000E+00 −2.162E+01 0.000E+00 0.000E+00 A4 −4.803E−02 −2.772E−01−5.245E−01 −1.352E−01 −4.715E−01 −1.807E−01 A6 4.930E−02 1.992E+003.697E+00 1.603E+00 4.522E−01 −5.912E−03 A8 −6.383E−01 −7.914E+00−1.223E+01 −4.061E+00 −6.013E−01 −2.470E−01 A10 8.364E−01 1.780E+012.417E+01 5.862E+00 1.127E+00 4.863E−01 A12 9.253E−01 −2.560E+01−3.265E+01 −6.945E+00 −8.323E−01 0.000E+00 A14 −2.960E+00 1.558E+012.091E+01 4.410E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10thSurface 11th Surface 12th Surface 13th Surface k 0.000E+00 −4.486E+000.000E+00 −8.657E+00 0.000E+00 0.000E+00 A4 1.240E−01 −2.468E−01−3.354E−01 −2.095E−01 6.702E−02 −1.832E−02 A6 −5.705E−03 3.425E−017.921E−02 1.026E−01 −1.109E−02 2.848E−03 A8 −4.473E−02 −1.684E−012.146E−02 −4.281E−02 −2.811E−04 −1.247E−03 A10 −1.349E−01 9.524E−02−1.326E−02 1.400E−02 2.589E−04 1.156E−04 A12 1.001E−01 −6.590E−023.203E−03 −3.099E−03 0.000E+00 0.000E+00 A14 0.000E+00 1.428E−02−9.607E−04 2.889E−04 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00

As shown in Table 6 below, the imaging lens in Example 3 satisfies allthe conditional expressions (1) to (11).

TABLE 6  (1) 0.5 < f1/f < 1.5 0.82  (2)−2.0 < f2/f < −0.5 −1.15  (3)0.3< f4/f < 1.0 0.52  (4)−1.5 < f5/f < −0.3 −0.69  (5)−3.0 < f6/f < −0.8−1.72  (6)0.3 < r4/f < 1.0 0.63  (7)20 < vd1 − vd2 < 50 31.66  (8)50 <vd3, vd4, vd5, vd6 < 80 vd3 56.16 vd4 55.57 vd5 56.16 vd6 56.16  (9)1.0< (r9 + r10)/(r9 − r10) < 2.7 1.84 (10)−1.5 < (r11 + r12)/(r11 − r12) <−0.5 −1.06 (11)0.3 < f4/f1 < 1.5 0.63

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6, eachaberration is corrected properly.

In Example 3, total track length TLA is 3.66 mm and TLA/(2ih) is 0.797,which suggests that the imaging lens is low-profile though it uses sixconstituent lenses. Also, the imaging lens offers a wide field of viewof 70 degrees or more and high brightness with an F-value of 2.2.

Example 4

The basic lens data of Example 4 is shown in Table 7 below.

TABLE 7 Example 4 in mm f = 3.03 Fno = 2.0 ω (°) = 37.0 ih = 2.30 TLA =3.66 bf = 0.74 Surface Data Curvature Surface Refractive Abbe SurfaceNo. i Radius r Distance d Index Nd Number vd (Object Surface) InfinityInfinity  1 (Stop) Infinity −0.208  2* 1.3099 0.444 1.544 55.57  3*9.4262 0.084  4* 5.6960 0.185 1.635 23.91  5* 1.6352 0.161  6* 2.29210.324 1.535 56.16  7* −90.0000 0.368  8* −1.4058 0.493 1.544 55.57  9*−0.7785 0.015 10* 3.1233 0.364 1.535 56.16 11* 1.2069 0.282 12* −1.99090.202 1.535 56.16 13* −90.0000 0.100 14 Infinity 0.210 1.517 64.20 15Infinity 0.499 Image Plane Infinity Constituent Lens Data Lens StartSurface Focal Length 1 2 2.745 2 4 −3.677 3 6 4.186 4 8 2.513 5 10−3.940 6 12 −3.811 Aspheric Surface Data 2nd Surface 3rd Surface 4thSurface 5th Surface 6th Surface 7th Surface k 1.449E+00 0.000E+000.000E+00 −1.687E+01 0.000E+00 0.000E+00 A4 −1.184E−01 −3.190E−01−6.755E−01 −1.772E−01 −3.241E−01 −8.044E−02 A6 1.481E−01 2.059E+003.825E+00 1.703E+00 4.171E−01 2.924E−02 A8 −9.474E−01 −7.415E+00−1.175E+01 −3.927E+00 −6.590E−01 −3.955E−01 A10 9.585E−01 1.734E+012.402E+01 5.926E+00 1.271E+00 5.636E−01 A12 9.423E−01 −2.544E+01−3.313E+01 −7.209E+00 −8.058E−01 0.000E+00 A14 −2.839E+00 1.524E+012.035E+01 4.510E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10thSurface 11th Surface 12th Surface 13th Surface k 0.000E+00 −4.031E+000.000E+00 −1.351E+01 0.000E+00 0.000E+00 A4 1.995E−01 −2.473E−01−3.320E−01 −1.637E−01 1.394E−01 −8.075E−03 A6 −1.690E−01 3.123E−017.333E−02 8.341E−02 −3.010E−02 −9.692E−03 A8 1.705E−01 −1.793E−01−1.069E−02 −3.566E−02 −7.976E−04 8.946E−04 A10 −1.021E−01 1.159E−01−1.693E−02 1.200E−02 1.262E−03 1.651E−04 A12 1.693E−03 −5.390E−023.760E−03 −3.468E−03 0.000E+00 0.000E+00 A14 0.000E+00 5.944E−033.890E−03 4.640E−04 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00

As shown in Table 8 below, the imaging lens in Example 4 satisfies allthe conditional expressions (1) to (11).

TABLE 8  (1) 0.5 < f1/f < 1.5 0.91  (2)−2.0 < f2/f < −0.5 −1.21  (3)0.3< f4/f < 1.0 0.83  (4)−1.5 < f5/f < −0.3 −1.30  (5)−3.0 < f6/f < −0.8−1.26  (6)0.3 < r4/f < 1.0 0.54  (7)20 < vd1 − vd2 < 50 31.66  (8)50 <vd3, vd4, vd5, vd6 < 80 vd3 56.16 vd4 55.57 vd5 56.16 vd6 56.16  (9)1.0< (r9 + r10)/(r9 − r10) < 2.7 2.26 (10)−1.5 < (r11 + r12)/(r11 − r12) <−0.5 −1.05 (11)0.3 < f4/f1 < 1.5 0.92

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8, eachaberration is corrected properly.

In Example 4, total track length TLA is 3.35 mm and TLA/(2ih) is 0.797,which suggests that the imaging lens is low-profile though it uses sixconstituent lenses. Also, the imaging lens offers a wide field of viewof 70 degrees or more and high brightness with an F-value of 2.0.

Example 5

The basic lens data of Example 5 is shown in Table 9 below.

TABLE 9 Example 5 in mm f = 3.04 Fno = 1.9 ω (°) = 37.0 ih = 2.30 TLA =3.79 bf = 0.73 Surface Data Curvature Surface Refractive Abbe SurfaceNo. i Radius r Distance d Index Nd Number vd (Object Surface) InfinityInfinity  1 (Stop) Infinity −0.231  2* 1.2919 0.464 1.544 55.57  3*9.5112 0.103  4* −90.0000 0.185 1.635 23.91  5* 2.2715 0.156  6* 1.78750.339 1.535 56.16  7* 3.8841 0.384  8* −2.0461 0.470 1.544 55.57  9*−0.7975 0.024 10* 4.0451 0.395 1.535 56.16 11* 1.1567 0.270 12* −2.52500.202 1.535 56.16 13* −90.0000 0.100 14 Infinity 0.210 1.517 64.20 15Infinity 0.488 Image Plane Infinity Constituent Lens Data Lens StartSurface Focal Length 1 2 2.695 2 4 −3.487 3 6 5.864 4 8 2.122 5 10−3.182 6 12 −4.863 Aspheric Surface Data 2nd Surface 3rd Surface 4thSurface 5th Surface 6th Surface 7th Surface k 1.180E+00 0.000E+000.000E+00 −3.988E+01 0.000E+00 0.000E+00 A4 −1.189E−01 −3.300E−01−5.911E−01 −2.267E−01 −4.740E−01 −8.678E−02 A6 2.084E−01 1.925E+003.735E+00 1.949E+00 6.112E−01 −3.541E−02 A8 −9.278E−01 −7.145E+00−1.145E+01 −3.987E+00 −8.311E−01 −1.616E−01 A10 6.950E−01 1.754E+012.427E+01 5.951E+00 1.093E+00 1.946E−01 A12 1.182E+00 −2.488E+01−3.306E+01 −7.638E+00 −6.223E−01 0.000E+00 A14 −2.285E+00 1.377E+011.911E+01 4.844E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10thSurface 11th Surface 12th Surface 13th Surface k 0.000E+00 −4.078E+000.000E+00 −1.128E+01 0.000E+00 0.000E+00 A4 1.671E−01 −2.140E−01−2.927E−01 −1.802E−01 1.015E−01 6.482E−03 A6 −7.483E−02 2.619E−014.191E−02 9.498E−02 −3.208E−02 −1.679E−02 A8 −1.059E−02 −1.652E−011.193E−02 −3.941E−02 1.555E−03 1.870E−03 A10 −1.642E−02 1.248E−011.096E−03 1.247E−02 5.870E−04 8.060E−05 A12 −2.668E−02 −6.201E−024.432E−03 −3.131E−03 0.000E+00 0.000E+00 A14 0.000E+00 8.068E−03−2.367E−03 3.715E−04 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00

As shown in Table 10 below, the imaging lens in Example 5 satisfies allthe conditional expressions (1) to (11).

TABLE 10  (1) 0.5 < f1/f < 1.5 0.89  (2)−2.0 < f2/f < −0.5 −1.15  (3)0.3< f4/f < 1.0 0.70  (4)−1.5 < f5/f < −0.3 −1.05  (5)−3.0 < f6/f < −0.8−1.60  (6)0.3 < r4/f < 1.0 0.75  (7)20 < vd1 − vd2 < 50 31.66  (8)50 <vd3, vd4, vd5, vd6 < 80 vd3 56.16 vd4 55.57 vd5 56.16 vd6 56.16  (9)1.0< (r9 + r10)/(r9 − r10) < 2.7 1.80 (10)−1.5 < (r11 + r12)/(r11 − r12) <−0.5 −1.06 (11)0.3 < f4/f1 < 1.5 0.79

FIG. 10 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 5. As shown in FIG. 10,each aberration is corrected properly.

In Example 5, total track length TLA is 3.72 mm and TLA/(2ih) is 0.809,which suggests that the imaging lens is low-profile though it uses sixconstituent lenses. Also, the imaging lens offers a wide field of viewof 70 degrees or more and high brightness with an F-value of 1.9.

Example 6

The basic lens data of Example 6 is shown in Table 11 below.

TABLE 11 Example 6 in mm f = 3.06 Fno = 2.2 ω (°) = 37.0 ih = 2.30 TLA =3.66 bf = 0.78 Surface Data Curvature Surface Refractive Abbe SurfaceNo. i Radius r Distance d Index Nd Number vd (Object Surface) InfinityInfinity  1 (Stop) Infinity −0.155  2* 1.3625 0.452 1.544 55.57  3*−14.0759 0.048  4* 50.5761 0.190 1.635 23.91  5* 2.3830 0.232  6* 3.60790.268 1.535 56.16  7* 3.4000 0.333  8* −2.6281 0.488 1.544 55.57  9*−0.6567 0.069 10* 2.4230 0.223 1.535 56.16 11* 0.7360 0.383 12* −2.56160.195 1.535 56.16 13* −80.3679 0.100 14 Infinity 0.210 1.517 64.20 15Infinity 0.542 Image Plane Infinity Constituent Lens Data Lens StartSurface Focal Length 1 2 2.308 2 4 −3.945 3 6 −200.330 4 8 1.481 5 10−2.073 6 12 −4.954 Aspheric Surface Data 2nd Surface 3rd Surface 4thSurface 5th Surface 6th Surface 7th Surface k 5.529E−01 0.000E+000.000E+00 −2.644E+01 0.000E+00 0.000E+00 A4 −4.475E−02 −3.264E−01−5.312E−01 −1.288E−01 −4.876E−01 −2.565E−01 A6 2.530E−02 2.073E+003.695E+00 1.594E+00 4.384E−01 1.183E−01 A8 −5.731E−01 −7.936E+00−1.211E+01 −3.988E+00 −4.459E−01 −2.816E−01 A10 7.221E−01 1.776E+012.411E+01 5.913E+00 1.118E+00 4.144E−01 A12 9.255E−01 −2.560E+01−3.265E+01 −6.945E+00 −8.321E−01 0.000E+00 A14 −2.960E+00 1.558E+012.091E+01 4.410E+00 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00 8th Surface 9th Surface 10thSurface 11th Surface 12th Surface 13th Surface k 0.000E+00 −4.677E+000.000E+00 −8.073E+00 0.000E+00 0.000E+00 A4 1.650E−01 −2.263E−01−3.285E−01 −2.039E−01 5.874E−02 −3.244E−02 A6 −6.893E−02 3.482E−017.124E−02 9.629E−02 −8.311E−03 6.388E−03 A8 −4.220E−03 −1.691E−011.991E−02 −4.098E−02 1.666E−04 −1.115E−03 A10 −8.912E−02 9.138E−02−1.178E−02 1.397E−02 1.675E−04 7.448E−05 A12 5.659E−02 −6.628E−023.772E−03 −3.311E−03 0.000E+00 0.000E+00 A14 0.000E+00 1.613E−02−1.021E−03 3.329E−04 0.000E+00 0.000E+00 A16 0.000E+00 0.000E+000.000E+00 0.000E+00 0.000E+00 0.000E+00

As shown in Table 12 below, the imaging lens in Example 6 satisfies allthe conditional expressions (1) to (11).

TABLE 12  (1) 0.5 < f1/f < 1.5 0.76  (2)−2.0 < f2/f < −0.5 −1.29  (3)0.3< f4/f < 1.0 0.48  (4)−1.5 < f5/f < −0.3 −0.68  (5)−3.0 < f6/f < −0.8−1.62  (6)0.3 < r4/f < 1.0 0.78  (7)20 < vd1 − vd2 < 50 31.66  (8)50 <vd3, vd4, vd5, vd6 < 80 vd3 56.16 vd4 55.57 vd5 56.16 vd6 56.16  (9)1.0< (r9 + r10)/(r9 − r10) < 2.7 1.87 (10)−1.5 < (r11 + r12)/(r11 − r12) <−0.5 −1.07 (11)0.3 < f4/f1 < 1.5 0.64

FIG. 12 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 6. As shown in FIG. 12,each aberration is corrected properly.

In Example 6, total track length TLA is 3.66 mm and TLA/(2ih) is 0.797,which suggests that the imaging lens is low-profile though it uses sixconstituent lenses. Also, the imaging lens offers a wide field of viewof 70 degrees or more and high brightness with an F-value of 2.2.

As explained above, the imaging lenses according to the Examples of thepresent invention are low-profile enough to meet the growing demand forlow-profileness, with total track length TLA of 4.0 mm or less and aratio of total track length TLA to maximum image height ih (TLA/2ih) ofabout 0.8, though they use six constituent lenses. In addition, theseimaging lenses offer a wide field of view of 70 degrees or more and highbrightness with an F-value of 1.9 to 2.2, correct aberrations properlyand feature low cost.

When any one of the imaging lenses composed of six constituent lensesaccording to the Examples of the present invention is used for anoptical system built in an image pickup device mounted in anincreasingly compact and low-profile mobile terminal such as asmartphone, mobile phone or PDA (Personal Digital Assistant), or a gameconsole or an information terminal such as a PC, or a home appliancewith a camera function, it contributes to the compactness of the imagepickup device and offers high camera performance.

The effects of the present invention are as follows.

According to the present invention, it is possible to provide a compactlow-cost imaging lens which offers brightness with an F-value of 2.5 orless and a wide field of view and corrects various aberrations properly,meeting the demand for low-profileness.

What is claimed is:
 1. An imaging lens which forms an image of an objecton a solid-state image sensor, comprising, in order from an object sideto an image side of the imaging lens: a first lens having positiverefractive power; a second lens having negative refractive power; athird lens having positive or negative refractive power and at least oneaspheric surface; a fourth lens that is a meniscus lens having positiverefractive power and an image-side surface that is convex near anoptical axis of the imaging lens; a fifth lens that is a double-sidedaspheric lens, the fifth lens having at least one surface withpole-change points separated from the optical axis; and a sixth lensthat is a meniscus lens having negative refractive power and anobject-side surface that is concave near the optical axis, wherein aconditional expression (8′) below is satisfied:50<νd3<80  (8′) where νd3: Abbe number of the third lens at d-ray. 2.The imaging lens according to claim 1, wherein a conditional expression(1) below is satisfied:0.5<f1/f<1.5  (1) where f: overall focal length of the imaging lens, andf1: focal length of the first lens.
 3. The imaging lens according toclaim 1, wherein a conditional expression (2) below is satisfied:−2.0<f2/f<−0.5  (2) where f: overall focal length of the imaging lens,and f2: focal length of the second lens.
 4. The imaging lens accordingto claim 1, wherein a conditional expression (3) below is satisfied:0.3<f4/f<1.0  (3) where f: overall focal length of the imaging lens, andf4: focal length of the fourth lens.
 5. The imaging lens according toclaim 1, wherein a conditional expression (4) below is satisfied:−1.5<f5/f<−0.3  (4) where f: overall focal length of the imaging lens,and f5: focal length of the fifth lens.
 6. The imaging lens according toclaim 1, wherein a conditional expression (5) below is satisfied:−3.0<f6/f<−0.8  (5) where f: overall focal length of the imaging lens,and f6: focal length of the sixth lens.
 7. The imaging lens according toclaim 1, wherein the third lens has a meniscus shape and an object-sidesurface that is convex near the optical axis.
 8. The imaging lensaccording to claim 1, wherein a conditional expression (6) below issatisfied:0.3<r4/f<1.0  (6) where f: overall focal length of the imaging lens, andr4: curvature radius of an image-side surface of the second lens.
 9. Theimaging lens according to claim 1, wherein conditional expressions (7)and (8) below are satisfied:20<νd1−νd2<50  (7)50<νd3,νd4,νd5,νd6<80  (8) where νd1: Abbe number of the first lens atd-ray, νd2: Abbe number of the second lens at d-ray, νd4: Abbe number ofthe fourth lens at d-ray, νd5: Abbe number of the fifth lens at d-ray,and νd6: Abbe number of the sixth lens at d-ray.
 10. The imaging lensaccording to claim 1, wherein conditional expressions (9) and (10) beloware satisfied:1.0<(r9+r10)/(r9−r10)<2.7  (9)−1.5<(r11+r12)/(r11−r12)<−0.5  (10) where r9: curvature radius of anobject-side surface of the fifth lens, r10: curvature radius of animage-side surface of the fifth lens, r11: curvature radius of theobject-side surface of the sixth lens, and r12: curvature radius of animage-side surface of the sixth lens.
 11. The imaging lens according toclaim 1, wherein a conditional expression (11) below is satisfied:0.3<f4/f1<1.5  (11) where f1: focal length of the first lens, and f4:focal length of the fourth lens.